1. Field of the Invention
The present invention relates to analog-to-digital converters, and more specifically to synchro-to-digital converters.
2. Description of the Prior Art
Various types of synchro-to-digital converters are known in the art.
Many of these prior art devices employ mechanical commutating means in which a commutator is attached to a rotatable shaft and coded so that a stationary sensing mechanism can detect a unique signal for any shaft displacement and translate this information into the desired signal format. However, such converters are bulky and subject to mechanical failure.
In another type of synchro-to-digital converter, the three-wire synchro signal is converted into two-wire sine and cosine equivalents. These signals are compared to determine the sector in which the angle to be measured lies and then converted into binary representations of the angle within that sector by means of successive approximations. Such devices produce an error function that is irregular and contains several discontinuities. Furthermore, such devices must be custom designed to encode a particular type of analog signal, and a separate channel must be supplied for each type of analog signal to be encoded.
U.S. Pat. No. 3,516,084 issued to Stephen J. Sacks and John E. Scott, entitled "Analog-to-Digital Converter", and assigned to the present assignee, concerns a synchro-to-digital converter in which the three-wire signal is converted into two-wire sine and cosine signals. The polarity of each of the sine and cosine signals as well as the relative magnitude of the two signals is determined and used to indicate the octant in which the angle corresponding to the input signal lies. Operational amplifiers are used to produce a linearized interpolation signal that can be encoded in conventional linear ratio encoders. Although this converter has great utility, the circuitry is relatively complex and not readily amenable to miniaturization.